1. Field of the Invention
The present invention relates to a dye-containing resist composition and a color filter using the same.
2. Description of the Related Art
As color filters for image sensing devices such as solid-state image sensing devices or liquid crystal display devices make possible to form fine patterns and therefore make possible to produce highly fine color filters, they are mainly produced by using a method of forming a pattern with a photoresist to which coloring matters are added. In this method, a resist composition comprising a coloring matter and a polymer resin is used, and a color filter is produced by repeating the following process for each color, in which the process comprises coating the composition on a substrate to form a film, patterning the colored layer with a photolithographic process, developing to form one colored pattern.
In the method, coloring matters used as colorant generally include pigments that are excellent in heat resistance and light resistance, and a resist in which a pigment is dispersed is proposed. For example, Japanese Patent Laid-open No. Hei 4-163552 discloses a photosensitive coloring resin composition characterized by comprising a resinous material curable with an acid, a photoacid generator and a pigment, in which the resinous material comprises a resin containing phenol and a crosslinking agent having N-methylol structure.
However, as the pigments contain particles having a size of about 1 μm itself, a fine pattern can not be formed due to an effect of these particles. Therefore, this makes difficult to produce color filters for charge coupled device (CCD) for which a high resolution is required.
On the other hand, when dyes are used as coloring matter, the dyes give homogeneous compositions as the dyes are soluble in organic solvents. Therefore, resist compositions in which dyes are used enable formation of fine patterns compared with a resist composition in which pigments are dispersed. For example, Japanese Patent Laid-open No. Hei 6-51514 discloses a negative type resist composition containing a resin material curable with an acid, a crosslinking agent, a photoacid generator, a dye and a solvent. The solvent includes for example methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol dimethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, N,N-dimethyl acetamide, N-metylpyrrolidone, γ-butyrolactone, cyclohexanone, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl lactate, ethyl lactate, ethyl pyruvate, dimethylformamide, and the like.
As dyes are generally low in solubility in organic solvents, it is difficult to increase the concentration of the dyes in resist compositions. In particular, when color filters in a shape of thinner film are requested, it is necessary to increase the concentration of dyes in resist compositions in order to realize a development of a prescribed emission spectrum. In addition, in case where a dye has a low compatibility with a resin, the dye becomes insoluble or is separated out while a resist composition is prepared from the dye, the resin and an organic solvent. Further, when a resist composition is restored, there are problems that a dye having a low solubility in an organic solvent is liable to be re-precipitated or re-crystallized, or that foreign matters (particles) are liable to occur.